Methods for forming an orthogonal end on a helical stent

ABSTRACT

A stent includes a continuous wave form having a plurality of struts and a plurality of crowns throughout the wave form. Each crown connects two adjacent struts. The wave form is wrapped around a longitudinal axis to define a central portion and two end portions located on opposite sides the central portion. The central portion includes a plurality of turns wrapped around the longitudinal axis and oriented at a first pitch angle relative to the longitudinal axis. The end portions each include a plurality of turns wrapped around the longitudinal axis and oriented at different pitch angles, and an end turn oriented at an angle relative to the longitudinal axis. The different pitch angles of the end portions are between the first pitch angle and the angle of the end turn relative to the longitudinal axis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority from U.S. ProvisionalPatent Application Ser. No. 61/243,597, filed on Sep. 18, 2009, theentire content of which is incorporated herein by reference. Thisapplication also claims the benefit of priority from U.S. ProvisionalPatent Application Ser. Nos. 61/243,578, 61/243,581, 61/243,582,61/243,592, and 61/243,600, all filed on Sep. 18, 2009, the entirecontents of all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to a method of manufacturinga helical stent having an orthogonal end relative to a longitudinal axisof the stent, as well as to a helical stent having an end that isorthogonal to the longitudinal axis of the stent.

2. Background of the Invention

A stent is typically a hollow, generally cylindrical device that isdeployed in a body lumen from a radially contracted configuration into aradially expanded configuration, which allows it to contact and supporta vessel wall. A plastically deformable stent can be implanted during anangioplasty procedure by using a delivery system that includes a ballooncatheter bearing a compressed or “crimped” stent, which has been loadedonto the balloon. The stent radially expands as the balloon is inflated,forcing the stent into contact with the body lumen, thereby forming asupport for the vessel wall. Deployment is effected after the stent hasbeen introduced percutaneously, transported transluminally, andpositioned at a desired location by means of the balloon catheter.

Stents may be formed from wire(s), may be cut from a tube, or may be cutfrom a sheet of material and then rolled into a tube-like structure.While some stents may include a plurality of connected rings that aresubstantially parallel to each other and are oriented substantiallyperpendicular to a longitudinal axis of the stent, others may include ahelical coil that is wrapped around the longitudinal axis at anon-perpendicular angle. Helical stents tend to have ends that are notperpendicular to the longitudinal axis due to the pitch of the helix. Tosquare off the ends of a helical stent, the last turn at either end mayinclude a wave form that includes waves of varying amplitudes. However,by varying the amplitudes of the waves, the stent may exhibitnon-uniform behavior as the stent is crimped onto a balloon and/orexpanded at the deployment site.

SUMMARY OF THE INVENTION

It is desirable to provide a helical stent that is configured tocontract and expand more uniformly, so that a “dog bone” effect duringexpansion may be substantially eliminated.

It is an aspect of the present invention to provide a method ofmanufacturing a stent. The method includes forming a wave form having aplurality of struts and a plurality of crowns. Each crown connects twoadjacent struts. The wave form has a central portion and two endportions located on opposite sides of the central portion. In anembodiment, some of the struts located in the end portions may havelengths longer than an average length of all of the struts of the waveform. In an embodiment, some of the struts located in the end portionsmay have lengths shorter than an average length of all of the struts ofthe wave form. The method includes wrapping the wave form about alongitudinal axis to define a plurality of turns so that a first turn isoriented at an angle relative to the longitudinal axis, a second turn isat a first pitch angle that is less than the angle that the first turnis disposed relative to the longitudinal axis, a third turn is at asecond pitch angle that is less than the first pitch angle, and a fourthturn is at a third pitch angle that is less than the second pitch angle.In an embodiment, the first turn is substantially perpendicular to thelongitudinal axis, i.e., the angle that the first turn is disposedrelative to the longitudinal axis is about 90°. In an embodiment, thefirst turn is not substantially perpendicular to the longitudinal axisand instead has a pitch angle that is greater than 90°, and the secondturn is at a pitch angle that is less than the pitch angle of the firstturn, and so on.

It is an aspect of the present invention to provide a stent thatincludes a wave form comprising a plurality of struts and a plurality ofcrowns. Each crown connects two adjacent struts within the wave form.The wave form is wrapped around a longitudinal axis to define a centralportion and two end portions located on opposite sides of the centralportion. The central portion comprises a plurality of turns oriented ata first pitch angle relative to the longitudinal axis. The end portionseach comprise a plurality of turns oriented at different pitch angles,and an end turn oriented substantially perpendicular to the longitudinalaxis. The different pitch angles of the end portions are between thefirst pitch angle and about 90°. In an embodiment, the end turn is notoriented substantially perpendicular to the longitudinal axis andinstead has a pitch angle that is greater than 90°, and the turns in theend portions have pitch angles that gradually transition from the pitchangle of the end turn to the first pitch angle.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 schematically depicts a stent according to an embodiment of thepresent invention in an unrolled configuration;

FIG. 2 schematically depicts a wave form for the stent of FIG. 1 beforethe wave form is wrapped around a longitudinal axis to define the stentof FIG. 1;

FIG. 3 schematically depicts a stent according to an embodiment of thepresent invention in an unrolled configuration;

FIG. 4 schematically depicts a stent according to an embodiment of thepresent invention in an unrolled configuration;

FIG. 5 schematically depicts an end turn of a stent according to anembodiment of the present invention in an unexpanded condition; and

FIG. 6 schematically depicts the end turn of the stent of FIG. 5 in anexpanded condition.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The following detailed description is merely exemplary in nature and isnot intended to limit the invention or the application and use of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

FIG. 1 illustrates a stent 10 according to an embodiment of the presentinvention. Although the stent 10 is generally cylindrical in shape andhas a longitudinal axis LA extending through the center of the stent 10,FIG. 1 illustrates the stent 10 in an “unrolled” state, which may becreated when the stent 10 is slit from one end to the other along anaxis that is parallel to the longitudinal axis LA. The stent 10 includesa continuous wave form 20, an embodiment of which is illustrated in FIG.2, that includes a plurality of turns 22 that are created when the waveform 20 is wrapped around the longitudinal axis LA during manufacturingof the stent 10. A mandrel or rod that is aligned with the longitudinalaxis LA may be used to support the wave form 20 as the wave form 20 iswrapped around the longitudinal axis LA. The stent 10 generally includesa central portion 24 and two end portions, a first end portion 26 and asecond end portion 28, that are located on opposite sides of the centralportion 24. In an embodiment, the first end portion 26 and the secondend portion 28 may be mirror images of each other.

As illustrated in FIG. 2, the wave form 20 includes a plurality ofstruts 30 and a plurality of crowns 32. Each crown 32 is a curvedportion or turn within the wave form 20 that connects adjacent struts 30to define the continuous wave form 20. As shown in FIG. 2, the struts 30are substantially straight portions of the wave form 20. In otherembodiments, the struts 30 may be slightly bent or have other shapes,such as a sinusoidal wave, for example.

As illustrated in FIG. 1, the wave form 20 is wrapped around thelongitudinal axis LA at different pitches so that the wave form 20generally defines a helical coil in the central portion 24 having afirst helical angle, or first pitch angle α, to define a first helix FH,and also defines ends that are substantially square or perpendicularwith the longitudinal axis LA. As illustrated, the first end portion 26,include a first turn 34 that is wrapped about the longitudinal axis LAat an angle β of about 90° so that the stent 10 has an end that issubstantially orthogonal or perpendicular to the longitudinal axis LA.In an embodiment, the angle β is greater than 90°.

The number of turns 22 about the longitudinal axis and the first helicalangle α may be determined by the particular specifications of the stent10, such as the desired unexpanded and expanded diameters and the lengthof the stent, as well as the size (e.g., diameter) and particularmaterial of the wire or strip of material that may be used to create thewave form 20. The illustrated embodiments are not intended to belimiting in any way.

The first end portion 26 also includes a second turn 36 that is acontinuation of the wave form 20 from the first turn 34. The second turn36 is wrapped about the longitudinal axis LA at a second pitch angle γthat is less than 90° but greater than the first pitch angle α, todefine a second helix SH. Additional turns may be part of the first endportion 26, such as a third turn 38, and a fourth turn 40, and may beconfigured to provide a more gradual transition between the first turn34 that is wrapped about the longitudinal axis LA at about 90° and thefirst pitch angle α of the central portion 24. In the illustratedembodiment, the third turn 38 is wrapped about the longitudinal axis LAat a third pitch angle Δ, which is greater than the first pitch angle αbut less than the second pitch angle γ, to define a third helix TH, andthe fourth turn 40 is wrapped about the longitudinal axis LA at a fourthpitch angle ε, which is greater than the first pitch angle α but lessthan the third pitch angle γ, to define a fourth helix QH. Althoughthree transitional turns 36, 38, 40 are illustrated in the embodiment ofFIG. 1, more or less transitional turns may be used. The illustratedembodiment is not intended to be limiting in any way.

As illustrated, each of the turns 34, 36, 38, 40 of the first endportion 26 include struts 30 having different lengths, and some of thestruts 30 have a length that is longer, labeled 30 a in FIG. 1, than theaverage length of all of the struts 30 of the stent 10. It is desirableto have the length of the longest strut 30 a of any given turn 34, 36,38, 40 to be as short as possible, yet provide the desired transition inpitch angle. The presence of the longer struts 30 a in the first endportion 26 allow for the transition from the orthogonal end to thehelical central portion 24, but may cause the stent 10 to expandunevenly, as compared to central portion 24, when an internal pressureis applied to the stent 10. It may be desirable to connect the crown 32that connects a longer strut 30 a within a turn 22 to a crown 32 of thenext turn in order to impede the expansion of the part of the wave form20 that contains the longer strut 30 a. In an embodiment, some of thestruts located in the first end portion 26 may have lengths that areshorter, labeled 30 b in FIG. 1, than an average length of all of thestruts 30 of the stent 10.

The stent 10 also includes a plurality of connections 50 that areconfigured to connect selected crowns 32 of adjacent turns 22 so thatwhen the stent is in an unexpanded condition, the plurality ofconnections 50 generally lie along a connection helix CH defined by aconnection helical angle θ relative to the longitudinal axis LA. Asillustrated in FIG. 1, the connection helix CH is oriented substantiallyopposite to the first helix FH described above such that the connectionhelical angle θ is between 0° and 90° when using a coordinate systemthat is opposite the coordinate system depicted in FIG. 1 (i.e., thepositive x axis runs from left to right rather than from right to left).

The connections 50 may be created by fusing the selected crowns 32together. As used herein, “fusing” is defined as heating the targetportions of materials to be fused together, without adding anyadditional material, to a level where the material in the targetportions flow together, intermix with one another, and form a fusionwhen the materials cool down to, for example, room temperature. Asuitable laser may be used to create the fusion.

In an embodiment, the connections 50 may be created by welding orsoldering the selected crowns 32 together. As used herein, “welding” and“soldering” are defined as heating an additional material that isseparate from the selected crowns and applying the heated additionalmaterial to the selected crowns 32 so that when the additional materialcools, the selected crowns 32 are welded or soldered together.

In an embodiment, the connections 50 may be created by fusing, welding,or soldering an additional piece of material (not shown) that extendsbetween selected crowns 32. The additional piece of material mayresemble a strut or a portion of a strut, and may be sized to providespacing between the selected crowns of two adjacent turns, if desired.The illustrated embodiments are not intended to be limiting in any way.

The size of the connections 50 may also be varied according to thedesired flexibility and rate of expansion for a given area of the stent10. In general, the larger the connection 50, i.e. the larger the fusionor weld, the greater the stiffness, and the slower the rate of expansionof the stent in the area of the larger connections.

FIG. 3 illustrates a stent 110 according to an embodiment of the presentinvention an “unrolled” state. The stent 110 includes a continuous waveform 120 that includes a plurality of turns 122 that are created whenthe wave form 120 is wrapped around the longitudinal axis LA duringmanufacturing of the stent 110. The stent 110 generally includes acentral portion 124 and two end portions, a first end portion 126 and asecond end portion 128, that are located on opposite sides of thecentral portion 124.

As illustrated in FIG. 3, the wave form 120 includes a plurality ofstruts 130 and a plurality of crowns 132. Each crown 132 is a curvedportion or turn within the wave form 120 that connects adjacent struts130 to define the continuous wave form 120. As shown in FIG. 3, thestruts 130 are substantially straight portions of the wave form 120. Inother embodiments, the struts 130 may be slightly bent or have othershapes, such as a sinusoidal wave, for example.

As illustrated in FIG. 3, the wave form 120 is wrapped around thelongitudinal axis LA at different pitches so that the wave form 120generally defines a helical coil in the central portion 124 having afirst helical angle, or first pitch angle α, to define a first helix FH,and also defines ends that are substantially square or perpendicularwith the longitudinal axis LA. As illustrated, the first end portion126, include a first turn 134 that is wrapped about the longitudinalaxis LA at an angle β of about 90° so that the stent 110 has an end thatis substantially square or perpendicular to the longitudinal axis LA. Inan embodiment, the angle β may be greater than 90°.

The number of turns 122 about the longitudinal axis and the firsthelical angle α may be determined by the particular specifications ofthe stent 110, such as the desired unexpanded and expanded diameters andthe length of the stent, as well as the size (e.g., diameter) andparticular material of the wire or strip of material. The illustratedembodiments are not intended to be limiting in any way.

The first end portion 126 also includes a second turn 136 that is acontinuation of the wave form 120 from the first turn 134. The secondturn 136 is wrapped about the longitudinal axis LA at a second pitchangle ρ that is less than 90° but greater than the first pitch angle α,to define a second helix SH. Additional turns may be part of the firstend portion 126, such as a third turn 138, and a fourth turn 140, and afifth turn 142, and may be configured to provide a more gradualtransition between the first turn 134 that is wrapped about thelongitudinal axis LA at about 90° and the first pitch angle α of thecentral portion 124. In the illustrated embodiment, the third turn 138is wrapped about the longitudinal axis LA at a third pitch angle π,which is greater than the first pitch angle α but less than the secondpitch angle ρ, to define a third helix TH. The fourth turn 140 iswrapped about the longitudinal axis LA at a fourth pitch angle ψ, whichis greater than the first pitch angle α but less than the third pitchangle π, to define a fourth helix QH. The fifth turn 142 is wrappedabout the longitudinal axis LA at a fifth pitch angle τ, which isgreater than the first pitch angle α but less than the fourth pitchangle π, to define a fifth helix NH.

As illustrated, each of the turns 134, 136, 138, 140, 142 of the firstend portion 126 include struts 130 having different lengths, and some ofthe struts 130 have a length that is longer, labeled 130 a in FIG. 3,than the average length of all of the struts 130 of the stent 110. It isdesirable to have the length of the longest strut 130 a of any giventurn 134, 136, 138, 140, 142 to be as short as possible, yet provide thedesired transition in pitch angle.

The presence of the longer struts 130 a in the first end portion 126allow for the transition from the orthogonal end to the helical centralportion 124, but may cause the stent 110 to expand unevenly, as comparedto central portion 124, when an internal pressure is applied to thestent 110. It may be desirable to connect the crown 132 that connects alonger strut 130 a within a turn 122 to a crown 132 of the next turn inorder to stiffen that area and impede the expansion of the part of thewave form 120 that contains the longer strut 130 a. In an embodiment,some of the struts located in the first end portion 126 may have lengthsthat are shorter, labeled 130 b in FIG. 3, than an average length of allof the struts 130 of the stent 110. By using additional transition turnsin the end portion 126 of the stent 110 illustrated in FIG. 3, ascompared to the end portion 26 of the stent 10 illustrated in FIG. 1,the longer struts 130 a illustrated in FIG. 3 may be shorter than thelonger struts 30 a illustrated in FIG. 1.

The stent 110 also includes a plurality of connections 150 that areconfigured to connect selected crowns 312 of adjacent turns 122 so thatwhen the stent is in an unexpanded condition, the plurality ofconnections 150 generally lie along a connection helix CH defined by aconnection helical angle θ relative to the longitudinal axis LA. Asillustrated in FIG. 3, the connection helix CH is oriented substantiallyopposite to the first helix FH described above such that the connectionhelical angle θ is between 0° and 90° when using a coordinate systemthat is opposite the coordinate system depicted in FIG. 3 (i.e., thepositive x axis runs from left to right rather than from right to left).

As also illustrated in FIG. 3, the end portions 126, 128 are notnecessarily mirror images of each other. The end portion 126 includes atotal of five turns 134, 136, 138, 140, 142, while the end portion 128only includes three turns 144, 146, 148. The end turn 144 of the endportion 128 has a pitch angle β of about 90° so that the end of the endportion 128 is substantially perpendicular to the longitudinal axis LA.In an embodiment, the end turn of the end portion 128 has a pitch anglethat is greater than 90°. The next turn 146 is wrapped about thelongitudinal axis LA at a pitch angle φ, which is less than the angle β(i.e., ˜90°), but greater than the first pitch angle α of the centralportion 124. The next turn 148 is wrapped about the longitudinal axis LAat a pitch angle ω, which is less than the pitch angle φ of the turn146, but greater than the first pitch angle α of the central portion124.

Of course, any number of transition turns may be in each end portion126, 128 to transition the helix of the central portion 124 to anorthogonal end. In an embodiment, the central portion of stent consistsof a series of transitions so that the entire stent is made up oftransitions and each turn includes struts of different lengths, and notwo adjacent turns have the same pitch angle. The illustratedembodiments are not intended to be limiting in any way.

The change in pitch angle from turn to turn within a transition, such aswithin the end portions 26, 28, 126, 128 discussed above and illustratedin FIGS. 1 and 3, is constant and can be calculated as the differencebetween the pitch angle of the end turn and the pitch angle of thecentral portion divided by the number of transition turns in between theend turn and the central portion, or:change in pitch angle=(β−α)/#transition turns  (1)Using equation 1, the various pitch angles for the turns 36, 38, 40 ofFIG. 1 and for the turns 136, 138, 140, 142, 146, 148 of FIG. 3 may becalculated. In an embodiment, the change in pitch angle between adjacentturns may not be constant.

FIG. 4 illustrates and embodiment of a stent 210 that is substantiallysimilar to the stent 10 of FIG. 1, but with additional end segments 212,214 that are connected to each end portion 26, 28 of the wave form 20.The end segments 212, 214 may be formed separate from the wave form 20and may be connected to the end portions 26, 28 of the wave form 20after the wave form 20 has been wrapped around the longitudinal axis LA.The end segments 212, 214 may be formed from a wire or other suitablestrip of material, or may be cut from a tube or sheet of material androlled into a ring-like structure.

As illustrated in FIG. 4, the end segment 212 includes a plurality ofstruts 230 having substantially the same length and a plurality ofcrowns 232 having substantially same size. Each crown 232 connectsadjacent struts 230 so as to form a continuous ring having a constantlength along the longitudinal axis LA. The end segment 212 may beconnected to the wave form 20 portion of the stent 210 with a pluralityof connections 250. In the illustrated embodiment, every crown 32 of theend portion 26 of the wave form 20 is connected to a corresponding crown232 of the end segment 212. The end segment 212 may assist incontrolling expansion of the areas of the end portion 26 that includethe longer struts 30 a so that the end of the stent 210 expands moreuniformly with the rest of the stent 210.

The end segment 214 may have substantially the same design as the endsegment 212, or the end segment 214 may have a different design tocompensate for the end of the wave form 20, as illustrated in FIG. 4.For example, the end segment 214 may include a longer strut 230 a tobridge a gap 240 that is created due to the end of the wave form 20.Other configurations of the end segment 212, 214 in accordance withembodiments of the present invention are contemplated, and theillustrated embodiment is not intended to be limiting in any way.

In addition to having the ends of the stent orthogonal to thelongitudinal axis LA of the stent, as well as having substantiallyuniform expansion properties upon deployment, it is also desirable forthe ends of the stent to be well opposed to the vessel wall when thestent is deployed at the target deployment site. It has been found thatthe greater the angle of strut deployment, the greater the propensity ofthe deployed struts to protrude outwardly. FIG. 5 illustrates an endturn 510 of a stent in accordance with an embodiment of the invention.The end turn 510 includes a plurality of struts 530 and a plurality ofcrowns 532 that connect adjacent struts 530 of the end turn 510 to eachother. In an embodiment, the end segment 212 of the stent 210 of FIG. 4includes the end turn 510 of FIG. 5.

The struts 530 and the crowns 532 are configured to provide a deploymentangle μ, illustrated in FIG. 6, of at least 40°. The deployment angle μis defined as the angle between the longitudinal axis LA of the stentand one of the struts 530 when the crowns 132 and struts 130 havestarted to plastically deform so that when the internal pressure isrelieved from the stent, the crowns 532 and struts 530 remain in thesame position and do not contract towards the longitudinal axis LA. Ithas been found that designing the crowns 532 and struts 530 to have adeployment angle of at least 40° allows the struts 530 to protrudeoutwardly from the outer circumferential surface of the rest of thestent (schematically depicted in FIG. 6 as line CS), which may allow theend of the stent to be well opposed to the vessel wall when the stent isdeployed at the target deployment site.

The embodiments of the stents discussed above may be formed from a wireor a strip of suitable material. In certain embodiments, the stents maybe formed, i.e., etched or cut, from a thin tube of suitable material,or from a thin plate of suitable material and rolled into a tube.Suitable materials for the stent include but are not limited tostainless steel, iridium, platinum, gold, tungsten, tantalum, palladium,silver, niobium, zirconium, aluminum, copper, indium, ruthenium,molybdenum, niobium, tin, cobalt, nickel, zinc, iron, gallium,manganese, chromium, titanium, aluminum, vanadium, and carbon, as wellas combinations, alloys, and/or laminations thereof. For example, thestent may be formed from a cobalt alloy, such as L605 or MP35N®, Nitinol(nickel-titanium shape memory alloy), ABI (palladium-silver alloy),Elgiloy® (cobalt-chromium-nickel alloy), etc. It is also contemplatedthat the stent may be formed from two or more materials that arelaminated together, such as tantalum that is laminated with MP35N®. Thestents may also be formed from wires having concentric layers ofdifferent materials. Embodiments of the stent may also be formed fromhollow tubes, or tubes that have been filled with other materials. Theaforementioned materials and laminations are intended to be examples andare not intended to be limiting in any way.

While at least one exemplary embodiment has been presented in theforegoing detailed description of the invention, it should beappreciated that a vast number of variations exist. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. Rather, the foregoingdetailed description will provide those skilled in the art with aconvenient roadmap for implementing an exemplary embodiment of theinvention, it being understood that various changes may be made in thefunction and arrangement of members described in an exemplary embodimentwithout departing from the scope of the invention as set forth in theappended claims.

What is claimed is:
 1. A stent comprising: a wave form comprising aplurality of struts and a plurality of crowns continuously throughoutthe wave form, each crown connecting two adjacent struts within the waveform, the wave form being wrapped around a longitudinal axis to define acentral portion and first and second end portions located on oppositesides of the central portion, the central portion comprising a pluralityof turns wrapped around the longitudinal axis and oriented at a firstpitch angle relative to the longitudinal axis, the first and second endportions each comprising a plurality of turns wrapped around thelongitudinal axis and oriented at different pitch angles, and an endturn oriented at an end turn angle of about 90° relative to thelongitudinal axis, at least one of the first and second end portionshaving pitch angles decreasing in size relative to the longitudinal axisas the plurality of turns transition from then end turn toward thecentral portion.
 2. The stent according to claim 1, further comprising aplurality of connections that connect selected crowns from adjacentturns of the wave form.
 3. The stent according to claim 2, wherein theconnections are fusions.
 4. The stent according to claim 2, wherein theconnections are welds.
 5. The stent according to claim 2, wherein atleast some of the connections are aligned along a helix at a pitch anglethat is opposite the first pitch angle.
 6. The stent according to claim1, wherein each end portion comprises at least one strut that is longerand/or shorter than an average length of the plurality of struts toaccommodate for the different pitch angles.
 7. The stent according toclaim 6, further comprising an end segment connected to the end turn,the end segment oriented substantially perpendicular to the longitudinalaxis and comprising a plurality of crowns and a plurality of struts, theplurality of struts having substantially the same length.
 8. The stentaccording to claim 7, wherein the end segment has a deployment angle ofgreater than about 40° relative to the longitudinal axis.
 9. The stentaccording to claim 1, wherein the wave form is formed from a wire. 10.The stent according to claim 1, wherein the wave form is formed from astrip of material.
 11. The stent according to claim 1, wherein the firstend portion comprises: a second turn that is a continuation of the endturn, the second turn is oriented at a second pitch angle, wherein thesecond pitch angle is less than the end turn angle but greater than thefirst pitch angle; and a third turn that is a continuation of the secondturn, the third turn is oriented at a third pitch angle, wherein thethird pitch angle is less than the second pitch angle but greater thanthe first pitch angle.
 12. The stent according to claim 11, wherein thesecond end portion comprises: a third turn that is a continuation of theend turn, the third turn is oriented at a third pitch angle, wherein thethird pitch angle is less than the end turn angle but greater than thefirst pitch angle; and a fourth turn that is a continuation of the thirdturn, the fourth turn is oriented at a fourth pitch angle, wherein thefourth pitch angle is less than the third pitch angle but greater thanthe first pitch angle.
 13. The stent according to claim 1, furthercomprising connecting selected crowns of adjacent turns withconnections.
 14. The stent according to claim 13, wherein the connectingcomprises aligning at least some of the connections along a connectionaxis defined by a connection angle, the connection angle oriented in anopposite direction as the first pitch angle relative to the longitudinalaxis.